# AcouS PROPA Software FAQ

*You will find answers below to some questions you ask and which we hope give you the information you seek . *

What is the meaning of "the assumption of diffuse reflection by walls" implementation in AcouS PROPA ?

This is how the reflection on the walls (soil, buidings,...) is considered. Reflection is called "specular" when the wave is reflected with an angle equal to the angle of incidence (that is, for example, optics in a mirror). Our model takes into account a diffuse reflection, i.e. the energy reflected from a wall is re-emitted in all directions, via a coefficient of directivity angle-dependent re-emission. This is a hypothesis that best represents reality, particularly in the external environment, where all the important parameters with respect to reflection tend to generate a diffuse reflection (different materials, many kinks and bumps, uneven surfaces...).

How are the sound sources modeled : assimilated to a point, to a line, to a surface, to a volume ?

Assimilated to a point when the source is small compared to the distance of propagation;

Linear, surface or volume depending on the ratio between the characteristic dimensions and the propagation distance, obtained by composing a number of point sources.

### Are buildings regarded as noise barriers (barriers to the propagation of noise) with an index of absorption and reflection ?

Our model calculates the attenuation by shielding effect of any obstacle placed between a source and a receiver (calculating the diffraction on edges of obstacles).

Moreover, each wall is characterized by a sound absorption coefficient. Each building and each floor element therefore participate in the propagation of sound or sound attenuation.

### Does the module "Calculation long-distance" take into account the compass ?

Yes, this module known as "weather" is integrated in AcouS PROPA® and it calculates the influence of the wind rose through the inclusion of meteorological information attached to the calculation, such as the direction, wind speed, temperature, etc...

The module "weather" affects the propagation of sound waves by bending them upwards (if the wind direction is opposite to the direction of sound propagation) or by pushing them down (if the wind and propagation of sound waves follow the same direction).

### Is it possible to make calculations for wind turbines, industries and buildings ?

Yes, AcouS PROPA® is capable of making calculations, whatever the nature of the site, open or closed (industrial, building or wind). The calculation of propagation is governed mainly by the strength and direction of sound sources, the direction and nature (absorption coefficient) of the walls and floor. You can make long distance calculations for a wind farm taking into account the influence of weather on the site.

### Is it possible to calculate, within a premise and radiate one or more walls outward, and calculate the surface level ?

Yes

### Is it possible to define, in addition to grid computing, specific points in order to calibrate with the measurements ?

Yes